The present invention relates to a digital contents copying inhibition apparatus which can prevent digital contents recorded in a music CD, a CD-ROM or the like from being copied into various types of recording media for inhibition of illegal distribution of the digital contents, a reproducible recording medium in which the digital data processed by the apparatus is recorded, a digital contents copying inhibition method, and a computer-readable recording medium in which a program for making a computer execute the method is recorded, and further to a reproducible recording medium in which the digital data processed by the method is recorded.
In recent years, because of the development in the fields of semiconductor integrated circuits and digital signal processing technology, size and cost of devices have been remarkably reduced, and especially in the field of entertainment, it has been becoming increasingly easier to enjoy contents of music or video images.
For example, in the case of musical contents, with consolidation of communication infrastructure, utilization of music provision services via wireless communications such as broadcasting or via a cable network has been becoming easier, but this type of services presume the real time utilization, so that the services do not sufficiently satisfy desires and needs of each audience, and are also restricted in terms of time and place. In order to make it possible for each user to enjoy a desired music at a desired time, it is necessary to store musical contents in recording media and distribute the recording media to each user. Such a system is beneficial not only for users, but also for providers of musical contents.
Records in which voice and sound recorded therein as analog signals which are expressed by irregularities in a spiral continuous groove and a magnetic disk with the analog signals for voices and sounds as changes in magnitude of magnetism were used for a long time. However, now days a music CD in which voice and sound are recorded in the form of digital bit arrays are widely used because it is excellent in portability and music reproducibility. With advent of the music CD, remarkable progresses has been made in the technology of recording and reproducing music as digital contents. Now a days, musical contents is provided with various types of recording media including the music CD such as DAT (Digital Audio Tape) or MD (Mini Disk).
Magnetic recording system is employed in DAT or MD. Therefore, a recording devices for such media can be provided at a relatively low price. The users can digitally record audio signals in these media. This means that musical contents provided with such media as the music CD can be copied into such media as a DAT and an MD because of its high reproducibility of digital data.
On the other hand, in the case of video contents, in association with popularization of scanners and digital cameras, there is now the general tendency for storing picture images or video images recorded on the conventional type of light-sensing films as a file (for still images and moving images) so that the image data can be searched for, managed, or edited later. Further, with appearance of low price and high quality printers, it has become possible to crease various types of designs such as drawings or drafts on a computer and print out the designs or to prepare and reproduce a computer animation film. Further, the digital image file can be recorded in a CD-ROM based on the same specifications as those for the music CD, and can be distributed in a wide area.
Also in recent years, in association with progress in computerization, number of end users has been rapidly increasing, and personal computers and peripheral devices for the computers have been provided with low prices. In this situation, it is possibly not only to reproduce a music CD with a computer, but also to easily obtain various recording media such as a hard disk or a CD-R each enabling storage of a relatively large volume of data.
An application program which is originally prepared for operating on a computer is also a type of digital contents. Such an application program is stored in a CD-ROM. Thus, the application program is not different from musical data stored in a music CD or digital image file in the point that the application program is digital data.
Popularization of computers and supply of digital contents together make it possible to copy musical data recorded in a music CD or a digital image file and an application program recorded in such recording media as a CD-ROM can into a hard disk, a CD-ROM or the like via a computer.
With rapid popularization of Internet and progress in the technology for compression of musical data or an image file, it has become easy to distribute the digital contents through a network, and the digital contents can be maintained and controlled only with a computer without purchasing a dedicated recording medium such as a music CD or a CD-ROM. In other words, at present, digital contents can easily be obtained and copied with a computer.
Further, it is possible to copy contents stored in some specific recording media such as a CD-ROM for game which is originally not intended to be reproduced on a personal computer via a personal computer into a CD-R. Such illegally copy of the digital contents has created a social problem.
In order to prevent digital contents from being illegally copied, various types of copying inhibition technologies have been developed and put into practical use. As a first example thereof, a recording device enabling storage making it possible to record digital data for a DAT or an MD has a copying inhibition function called as SCMS (System Copy Management System) from a view point of copy right protection. This copying inhibition function is realized by recording code (a copying inhibition bit) for inhibition of copying in a recording area for control on DAT or MD. For instance, at first, when recording (copying) is executed for MD, a copying inhibit bit indicating that copying is allowed only once is written therein. When recording is tried by a user using the MD with digital contents and the above-described copying inhibition bit written and copied therein as a copied medium, the user""s recording device detects the copying inhibition bit, and inhibits recording. Namely, with this function, generation of additional copies is prevented.
As a second example of the copying inhibition function, there is known the ID code authorization method in which input of ID code is required when an application program stored in a CD-ROM is installed in a computer. When this method is employed, unless a user who has obtained a CD-ROM through a legal route acquires the ID code from the provider of the CD-ROM and input the ID code, installation of the CD-ROM is never completed. With this feature, a user who obtained only a CD-ROM illegally copied can not execute the application program, which in turn prevent distribution of illegal copies.
Especially when executing shareware distributed through a network, in most cases, a password which corresponds to the ID code described above is required to cancel inhibition of trial use, and this password can be acquired by paying a fee or the like to a provider of the shareware. In the case of shareware, however, as it is allowed to freely download shareware from a server on the network, which means in a broad sense that it is allowed to freely copy the shareware, so that the authorization of a user with a password is not for preventing digital data from being copied.
Further, there is a case where the ID code is recorded in a CD-ROM and input of ID code by the user is not required. For instance, in a case of a game machine, the ID code is recorded in a pregap section in the utmost inner groove of a CD-ROM for game machine, and the game machine determines by reading the ID code recorded in the pregap section whether the CD-ROM is a legal one or not. Any data can not be read out from, nor written in this pregap section with an ordinary CD-R drive which can be used in a personal computer, and as a result, a CD-ROM for game machine is prevented from being illegally copied.
As a third example of the copying inhibition technology, the ciphering technology is known. In the ciphering technology, digital data which is a collection of FIGS. 0 and 1 is mathematically converted so that the ciphered data can not be deciphered without using a particular key and algorithm. In other words, even when digital contents having been subjected to ciphering is obtained, so long as the key is not acquired, the digital contents can not correctly be reproduced, which prevents distribution of illegal copies of the digital contents.
As a fourth example of copying inhibition technology, the electronic watermark technology is known. In this technology, specific information such as copy right is buried in the entire digital contents to enable identification of a source of an illegal copy or detection of falsified data, and this technology utilizes the fact that musical data or image data include a portion or portions which can not be sensed by human.
The copying inhibition technologies described above have problems as described below. The copying inhibition function of a recording apparatus described as the first example above can prevent repetition of illegal operations for copying between recording apparatus each having the copying inhibition function, but when digital contents is recorded via a computer in a hard disk or in other types of media, it is easy to suppress the function, and in that case, illegal operations for copying the original contents can be repeated endlessly.
For instance, even in a case of DAT or MD in which a copying inhibition bit is written in with a recording apparatus, it is easy to prepare a program which can ignore presence of the copying inhibition bit when a regenerated signal (a digital signal or an analog signal) outputted from a device for reproducing the DAT or MD is recorded in a recording media such as a hard disk.
Especially, this copying inhibition function is not for modifying digital contents for inhibition of copying, and the copying inhibition bit is introduced only as a flag, so that an operation for copying digital contents can be repeated endlessly only by skipping detection of the copying inhibition bit.
Further, a DAT recording apparatus produced immediately after popularization of DAT started do not have the coping inhibition function, and it is possible to repeat operations of copying digital contents with the old type of recording apparatus by using a recording medium in which the digital contents was recorded once.
In the case of ID code authorization method described as the second example above, as it is necessary to acquire ID code independently from a CD-ROM when the application program is installed. Effect of inhibition of illegal operation for copying digital contents is expected, but actually there is a problem that the ID code is often distributed with an illegally copied CD-ROM. Especially, after the application program is installed, the ID code is not required except the case where user support is provided from a provider of the application program. Namely, with this ID code authorization method, it is impossible to completely inhibit the operation for copying digital contents recorded in a CD-ROM legally obtained.
With the password authorization method used for shareware, like in the case of ID code described above, it is impossible to completely inhibit the operations for copying digital contents once legally obtained by using the password.
In the case of game machine described above, there is the problem that there are distributed copying-protection canceling devices which can replay, like the regular CD-ROM for game machine, a CD-R prepared by copying digital contents which is originally prepared as copying-allowable and recorded in a CD-ROM, namely by copying only the contents from a CD-ROM dedicated to a game machine (a portion excluding the ID code recorded in the pregap section). This copying-protection canceling apparatus cancels the copying protection by skipping the step of authorization of ID code recorded in the pregap section and forcefully sending a signal indicating that the CD-ROM is a legal one to a CPU of the game machine, and resultantly this scheme allows the operation for illegally copying digital contents recorded in a CD-ROM for game machine.
The ciphering technology described as the third example above can be for insuring security of data in a document file, for enabling the secret talk function in digital telephone, for accounting for chargeable broadcasting, and further for scrambling digitized musical data or video data, but when a great volume of data is to be ciphered, a long time is required for encoding and decoding, and this technology is not suited to huge data or a big program.
The electronic watermark technology described as the fourth example above enables identification of a source of illegal copies and detection of falsified data, but the technology allows endless repetition of the operation for copying digital contents, and further also the copied contents can be reproduced or visually checked, which means that the illegal operation for copying digital contents is substantially allowed.
It is an object of the present invention to provide a digital contents copying-inhibition method which can physically inhibit illegal operation of copying digital contents such as music pieces or programs and also which can effectively limits use of digital contents once copied by a method different from conventional technologies such as the ID code authorization technology or ciphering technology, and also to provide a computer-readable recording medium in which a program for making a computer execute the program is recorded.
The digital contents copying-inhibition apparatus according to the present invention comprises a guard data storage section in which guard data to be appended to a digital data such as sound and image and sensed only in reproduction after the digital data is compressed is stored, a data analysis section which identifies a position of a digital value having a prespecified increase data and also a prespecified amplitude in digital data as a peak position, sets a flag for a digital value at a position by a prespecified number away from the peak position, and sets a plurality of digital values extending over a range centering on the digital value position for which the flat is set as a data pattern, and a guard data appending section which modifies the digital data by appending the guard data to the position where the data pattern is present.
Other objects and features of this invention will become apparent from the following description with reference to the accompanying drawings.